dt-bindings: net: Add bindings for AX88796C SPI Ethernet Adapter

Add bindings for AX88796C SPI Ethernet Adapter.
Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/asix,ax88796c.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/asix,ax88796c.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ASIX AX88796C SPI Ethernet Adapter
+
+maintainers:
+  - Łukasz Stelmach <l.stelmach@samsung.com>
+
+description: |
+  ASIX AX88796C is an Ethernet controller with a built in PHY. This
+  describes SPI mode of the chip.
+
+  The node for this driver must be a child node of an SPI controller,
+  hence all mandatory properties described in
+  ../spi/spi-controller.yaml must be specified.
+
+allOf:
+  - $ref: ethernet-controller.yaml#
+
+properties:
+  compatible:
+    const: asix,ax88796c
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 40000000
+
+  interrupts:
+    maxItems: 1
+
+  reset-gpios:
+    description:
+      A GPIO line handling reset of the chip. As the line is active low,
+      it should be marked GPIO_ACTIVE_LOW.
+    maxItems: 1
+
+  local-mac-address: true
+
+  mac-address: true
+
+required:
+  - compatible
+  - reg
+  - spi-max-frequency
+  - interrupts
+  - reset-gpios
+
+additionalProperties: false
+
+examples:
+  # Artik5 eval board
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/gpio/gpio.h>
+    spi0 {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ethernet@0 {
+            compatible = "asix,ax88796c";
+            reg = <0x0>;
+            local-mac-address = [00 00 00 00 00 00]; /* Filled in by a bootloader */
+            interrupt-parent = <&gpx2>;
+            interrupts = <0 IRQ_TYPE_LEVEL_LOW>;
+            spi-max-frequency = <40000000>;
+            reset-gpios = <&gpe0 2 GPIO_ACTIVE_LOW>;
+        };
+    };